When a manager wants someone to quit but doesn't want to fire them, he gets them to quit by either discussing the negatives of the position with no solution or positives, or he tells them they wont be successful and displays no confidence in their ability to succeed unit they quit.

After Kevin Grissom knocked up his secretary, he wanted to fire her. He knew it was illegal to fire her for that reason, but knew it was necessary. As a solution he explained to her that the negatives of the position far outweighed any positives and that she should think about that. Consequently, she quit, saving KGrissom from the headache of working with her everyday. It was a textbook quitfire right out of management 101.